Summary Distribution and gradient analysis of Ink disease caused by Phytophthora cambivora were studied over a 2 years period in a chestnut forest in Italy. Ink disease incidence, severity and tree mortality increased during the period over the studied chestnut forest. Disease descriptors and landform datasets were analysed by Geographic Information System software and displayed as a multilayer thematic map. Indices of dispersion and empirical dispersion models were used to study spatial distribution of disease in the investigated area. Semivariograms were used to interpolate spatial data and to map Ink disease. A logical spatial dependence of the studied variables was found. Ink disease occurred preferentially along natural drainages routes where multicyclic inoculum build up was likely to occur. A negative relationship was found between Ink disease incidence, severity and tree mortality with respect to distance from the drainage.